Optical communications have been fostered by passive alignment techniques which eliminate a substantial portion of active alignment of an optoelectronic device to an optical waveguide. Typical examples of such alignment techniques are with a laser aligned to an optical fiber or planar waveguide. While offering a great deal of precision, active alignment is very labor intensive, and accordingly results in a very high cost end product. The desire is for a high precision alignment, without the attendant disadvantage of cost associated with active alignment. One such technique for passive alignment as a low cost replacement for active alignment is found using silicon waferboard (SWT) technology. In silicon waferboard technology, a substrate of preferably monocrystalline material is selectively etched to effect alignment fiducials as well as grooves for reception of optical fibers.
One such example of passive alignment in silicon waferboard technology is disclosed in U.S. Pat. No. 5,163,108 to Armiento et al., the disclosure of which is incorporated by reference. This reference discloses a notch for passive alignment of an optoelectronic device to alignment fiducials, pedestals and standoffs, located on the silicon waferboard substrate. Such an alignment scheme is as shown in FIG. 1. As can be seen, the alignment notch 101 on the laser bar 102 has a substantially right angle orientation. The pedestals 103 and standoffs 104 which facilitate alignment of the laser bar in the x, y plane and z direction, respectively, are also of a right angle orientation as is shown. While such an apparatus for the alignment of an optoelectronic device to an optical fiber or planar waveguide has definite merit when compared to active alignment techniques, there is a potential disadvantage due to the limitation of the precision etch. To this end, tolerances for the notch location relative to the laser mode are on the order of 0.1 to 0.2 microns for passive alignment assemblies suitable for single mode optical fiber alignment. Typically, the technology for locating etched notches in laser wafers is .+-.0.2 to 0.5 microns in precision at best, so it can be seen that the potential for manufacturing yield loss is great. To this end, the degree of freedom afforded the right angle notch and pedestal/standoff alignment fiducials is not great enough when compared to the required tolerances for passive alignment assemblies given the current state of precision etching techniques. Accordingly, because a single wafer of semiconductor lasers is relatively expensive, the overall cost per part is correspondingly higher as the manufacturing yield is reduced by unacceptable alignment.
What is needed is an alignment scheme in a passive manner where aligning an optoelectronic device to an optical waveguide using silicon waferboard technology has a greater degree of freedom to enable an overlap of the alignment tolerances of single mode applications with the etching precision limitations of standard technology.